This invention relates to a disk apparatus and, more particularly, a disk apparatus for reproducing data from a CAV type disk and M-CAV type disk and for recording data thereon.
In a disk apparatus, for example, an optical disk apparatus, an optical disk is used for recording data on a spiral track. Recording or reproduction of data in or from the optical disk is performed by an optical head, which is moved linearly by a linear motor in the radial direction of the optical disk.
The recording and reproduction of data in the optical disk apparatus are usually performed using a CAV (constant angular velocity) type disk or a CLV (constant linear velocity) type disk. In the CAV type disk, the angular velocity of the optical disk is held constant, to ensure steady recording or reproduction and to reduce access time. Further, in the CAV type disk, the recording or reproduction timing, i.e., the demodulation or modulation frequency, is constant. In the CLV type disk, on the other hand, the angular velocity of the optical disk for recording or reproduction is reduced as the optical head is moved toward the outer periphery of the optical disk, to obtain a constant linear velocity of the optical disk track with respect to the optical head. The CLV type disk is capable of high-density recording of data. However, since the angular velocity of the optical disk for recording and reproduction of data is varied with the movement of the optical head in the radial direction of the optical disk, it takes some time until the angular velocity of an optical disk drive motor is stabilized. In addition, the motor cannot be operated at high angular velocity. Therefore, this results in considerably longer access times, and the data transfer rate is inevitably reduced.
To obtain reduced access times, increased recording capacity, and increased data transfer rates, a modified constant angular velocity (M-CAV) system is used, in which the optical disk is rotated at a constant angular velocity while the recording or reproduction timing, i.e., the demodulation or modulation frequency, is varied according to the access position, thus achieving satisfactory recording or reproduction.
The presently available optical disk apparatus, however, are used with either CAV type optical disk or M-CAV type optical disk alone, that is, there is no optical disk apparatus which can be used with both types of optical disks. Accordingly, demand has arisen for a disk apparatus which can be used with optical disks of both these systems.